Hairpinning

Overview

Alcatel-Lucent 1665 DMX supports both inter-function group, intra-function group, intra-port as well as pass-through hairpinning cross-connections. These capabilities allow you to route traffic in and out of Alcatel-Lucent 1665 DMX without consuming bandwidth on the high-speed (OC-3/12/48/192) interfaces, and to host multiple rings on the low-speed interfaces of the Alcatel-Lucent 1665 DMX shelf (OC-48, OC-12, OC-3).

Inter-function group hairpin

In a "hairpinning" topology, low-speed tributary traffic is routed into the system and back out of the system without ever being placed on the high-speed (OC-12/48/192) UPSR interfaces (this description assumes that the MAINs are provisioned for UPSR protection, but intra-function group hairpins are supported on all MAIN application/protection schemes). The cross-connection capability of connecting any input on a circuit pack in a function or growth slot to any output on a circuit pack in a different function or growth slot of the same shelf allows you to use a combination of add/drop and hairpinning of compatible payloads through a variety of interfaces. You can bring traffic in from one remote site and cross-connect it at the VT, STS-1, STS-3c, STS-12c, STS-48c, , or STS-192c level back out to other remote sites without consuming any capacity on the high-speed UPSRs.

The figure below demonstrates a topology in which traffic is hairpinned among OC-12 and OC-3 low-speed interfaces (OC-48 also an option). For instance, a signal dropped from the OC-3 UPSR in the bottom left of the figure can travel out of Alcatel-Lucent 1665 DMX on the OC-12 UPSR on a completely different tributary.

Figure 3-36: Inter-function group hairpin

Low-speed ring closure

Alcatel-Lucent 1665 DMX can host multiple rings on the low-speed interfaces of the Alcatel-Lucent 1665 DMX shelf. This is accomplished by either protected drops from a UPSR or UPSR pass-throughs. Alcatel-Lucent 1665 DMX can close a low-speed ring by supporting a cross-connection between a receive port on one circuit pack and a corresponding transmit port on another companion circuit pack in the same function or growth group (cross-connections can also be made to ports in any other slot on the shelf). All protection switching advantages/capabilities of UPSR configurations still apply in the low-speed ring closure application shown below.

The figure below demonstrates a ring closure topology in which both an OC-3 or OC-12 ring is being hosted on the low-speed interfaces alone. Notice that this consumes no bandwidth on the OC-48, high-speed UPSR in the top of the figure.

Figure 3-37: Low-speed ring closure

Intra-function group hairpin

Alcatel-Lucent 1665 DMX supports intra-function group, hairpin cross-connections that are cross-connections between different tributaries on different ports within the same function group. Again, the application above could be enabled by either intra-function group hairpins or UPSR pass-throughs. Intra-function group hairpins are available in all protection schemes, not just in UPSR applications.

Intra-port hairpin

Alcatel-Lucent 1665 DMX supports the provisioning of intra-port cross-connection on UPSR interfaces. Intra-port characterizes cross-connections between channels/time slots/tributaries hosted on the same port.